Ships are fast becoming the largest source of air pollution in the EU. Unless more action is taken, by 2020, they will be a more significant source of gas and particulate pollution than all land sources combined.
As a result, the International Maritime Organization (IMO) has strengthened its requirements for reduction of emissions of sulfur oxides (SOx) and particulate matter (PM) (59th session of the Marine Environment Protection Committee, 16 Jul. 2009). While one method for reducing SOx emissions is the use of low-sulfur fuels, IMO regulations allow as an alternative the use of technologies that abate the sulfur content in the emitted gas.
Wet scrubbers using sodium hydroxide solution are widely used in flue gas desulfurization (FGD). Since equipment size is particularly critical on board ships, where the available space is limited, it is critical that the apparatus be as economical of space as possible while maximizing the contact between the liquid and the flue gas. Other factors limiting a wet scrubber for use on board a ship include weight and electrical power limitations. Typical wet scrubbers remove some 80% of the SOx from the flue gas. In many cases, this amount of SOx reduction is not sufficient.
Japanese Pat. No. 8281055 discloses a flue gas scrubbing apparatus in which gas entering the scrubber flows in a circular motion about the circumference of an exhaust pipe. U.S. Pat. No. 4,273,750 discloses a similar method for a dry flue gas scrubber. U.S. Pat. No. 4,334,897 discloses a wet flue gas scrubbing apparatus in which gas-liquid contact is maximized by forcing the gas through a series of baffles. This apparatus, however, is not particularly compact or simply designed.
To date, most applications have utilized one scrubber per source. Most of these scrubbers are “spray tower” types with large volumes and relatively low gas flow speeds. Thus, there remains a long-felt need for a wet flue gas scrubber that is efficient, compact, and of straightforward design, in particular, one that meets these technical requirements while being sufficiently compact to be used, e.g., on board a ship.